Health officials warn that a new case of Ebola in central Africa is a “major, major game-changer.” Two years after the worst Ebola epidemic in history finally subsided, the virus is surging again. A now-deadly in Democratic Republic of Congo has now spread to a city.

A report of an Ebola in the city of Mbandaka, meaning the virus has arrived in a densely populated area. Until today, the 44 possible cases and 23 deaths have been limited to the remote rural area of Bikoro. But Bikoro lies near the heavily traveled Congo River, which connects travelers not only to Mbandaka to the north, but to the capital city of Kinshasa, with more than 9 million residents, to the south.

The fear is if the virus reaches large urban areas, it could spread quickly, with devastating consequences.

In 2014, a major Ebola epidemic in west Africa killed more than 11,000 people. Since then, an experimental vaccine has been developed, and 4,000 doses have arrived in the Congo, with thousands more to follow. The plan is to immunize the more than 500 contacts of infected people in an attempt to stop the virus from spreading.

This time, health officials are all over this. They are coordinating their efforts – and that includes not only tracking down and monitoring contacts of infected people, but a plan to give those contacts the experimental vaccine. Health officials are determined to do everything possible to avoid repeating the mistakes of 2014.